The IETF is forming a new working group for an open video codec[1]. It is still a BoF and will be chartered in 3-6 months, which is when the real work will begin. More details on the charter can be found in this email [2].
As for the audio, WebRTC chose G.711 and Opus as mandatory to implement (MTI)[3]. The reason for G.711 is so that WebRTC can interoperate with legacy devices.